<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box1 {
            width: 100px;
            height: 100px;
            border-radius: 50%;
            background-color: #bfa;

            animation: ball 1s ease-in forwards;
        }

        .outer {
            height: 500px;
            border-bottom: 10px solid #111111;
            margin: 50px auto;
            overflow: hidden;
        }

        @keyframes ball {
            from {
                margin-top: 0;
            }
            33%,to{
                margin-top: 400px;
                animation-timing-function: ease-out;
            }
            66%{
                margin-top: 100px;
            }

        }
    </style>
</head>
<body>
<div class="outer">
    <div class="box1"></div>
</div>
</body>
</html>